The body surfaces of jewel beetles and other beetles create colors by reflecting lights at different wavelengths.

"The Buprestid beetles…as well as many ground-beetles (Carabidae), are different again in that the body surface producing the colour is hardened and quite permanent and sculptured into subtly varying shapes that reflect light at different wavelengths - blue, purple, green, bronze, silver and gold. The purple flush on the elytra of the ground-beetle, Carabus violaceus, is due to this cause, as are the metallic marks on various butterfly pupae." (Wootton 1984:140)